Cycloocta-1,5-diene complexes platinum

Significant advances in organonickel chemistry followed the discovery of frtzws,fraws,fraws-(l,5,9-cyclododecatriene)nickel, Ni(cdt), and bis(l,5-cycloocta-diene)nickel Ni(cod)2 by Wilke et. al.1 In these and related compounds, in which only olefinic ligands are bonded to the nickel, the metal is especially reactive both in the synthesis of other compounds and in catalytic behavior. Extension of this chemistry to palladium and to platinum has hitherto been inhibited by the lack of convenient synthetic routes to zero-valent complexes of these metals in which mono- or diolefins are the only ligands. Here we described the synthesis of bis(l,5-cyclooctadiene)platinum, tris(ethylene)-platinum, and bis(ethylene)(tricyclohexylphosphine)platinum. The compound Pt(cod)2 (cod = 1,5-cyclooctadiene) was first reported by Muller and Goser,2 who prepared it by the following reaction sequence ... 

Nothing is known about the chelating tendencies of cydoocta-l,3-diene and cycloocta-1,4-diene with platinum(II). Methanolic Na2PdCU reacts with the 1,3-diene at room temperature to give a methoxy-substituted ir-allyl complex, while on heating ir-cycloocta-2,4-dienylpalladium(II) chloride is formed 122). The latter is also obtained from the diene and PdCl2 in acetic acid 82). Both complexes are similar to their cyclohepta-1,3-diene analogs (Section II, D). 

There have been reports of syntheses of cyano complexes in fused potassium cyanide, though the characterization of the products has not always been satisfactory.1 The dry reaction between potassium cyanide and potassium hexaiodoplatinate(IV), however, certainly gives the impure hexacyano-platinate(IV) and substitution of cycloocta-1,5-diene bonded to platinum(II) may be achieved by the use of solid potassium cyanide in the presence of a crown ether catalyst.16... 

As shown in eqs. (21.3) and (21.4), the reactions of platinum halides with diolefins afford diolefin platinum complexes. In these diolefin platinum complexes, the order of the stability of the four compounds is shown in Figure 21.1 [18]. The figure shows that the complexes of cyclic diolefins, such as cycloocta-1,5-diene and dicyclopentadiene, are more stable than those of linear unsaturated compounds. 

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